Wireless local area networks (WLANs) have become more popular because of their convenience and flexibility. As new applications for such networks are being developed, their popularity is expected to significantly increase.
Institute of Electrical and Electronics Engineers (IEEE) working groups have defined an IEEE 802.11 baseline standard having extensions which are intended to provide higher data rates and other network capabilities. Under the IEEE 802.11 standards, network entities include a management information base (MIB). The MIB may be either a media access control (MAC) layer MIB or a physical (PHY) layer MIB. Data entries in a MIB table use IEEE 802.11 standards.
Network management entities (NMEs), connected to a WLAN, communicate with each other by sending frames. There are three types of MAC frames defined by the 802.11 standards: 1) data frames; 2) control frames; and 3) management frames. There also sub-types for each of these frames. For example, an action frame is a subtype of a management frame. Action frames are further defined by categories. Currently, action frame categories are defined as follows: 0—spectrum management: 1—quality of service management; 2—direct link protocol; and 3—radio measurement.
A service primitive is an internal signaling message used for inter-layer or inter-protocol entity exchanges, such as between a station management entity (SME) and a MAC layer management entity (MLME), with standardized message contents. Although a particular format of message is not specified by the standards, the standards do specify the content. Service primitives are typically used to initiate, confirm or report a particular action, such as by sending a particular frame for management purposes from one WTRU to another WTRU.
In accordance with IEEE 802.11 standards, an SME is incorporated into the WTRU order to provide correct MAC operation. The SME is a layer-independent entity that may be viewed as residing in a separate management plane or as residing “off to the side.” Thus, the SME may be viewed as being responsible for such functions as the gathering of layer-dependent status from the various layer management entities, and similarly setting the value of layer-specific parameters. The SME typically performs such functions on behalf of general system management entities and, implements standard management protocols.
Furthermore, according to IEEE 802.11 standards, a WTRU contains configuration settings in the MIB that control its behavior. It is important for an AP to be able to understand the configuration of each WTRU in order to interpret the WTRU's behavior and to improve performance in the context of WLAN radio resource management (RRM). For example, a WTRU keeps track, in its MIB, of successfully received but not decodable data frames. This is important information for an AP to provide a minimum level of quality of service to the WTRU.
RRM is one of the most important aspects in WLAN management. A WLAN can achieve significant performance enhancement by performing RRM, including in-band interference mitigation and frequency re-use. For efficient RRM, it is necessary for an NME to retrieve WTRU specific TPC related information. A problem with the MIB data structure used in conventional wireless systems is that TPC information of a WTRU is not stored in the MIB of an AP.
Interference mitigation is a classic technique used in wireless communication systems to avoid interfering with other users in the vicinity by minimizing the amount of transmission power. The IEEE 802.11h standard defines messaging of a maximum allowable transmit power by means of BEACON and PROBE RESPONSE frames, and messaging by means of TPC REQUEST and TPC REPORT frames to get the instantaneous transmit power and link margin. An AP broadcasts a BEACON frame, or replies with a PROBE RESPONSE frame. A BEACON frame contains a country field, a power constraint field, a transmit power field, and a link margin field. The country field contains the maximum regulatory power level. The power constraint field contains an offset value compared to the maximum regulatory power level. The transmit power field indicates the transmit power used to transmit the TPC REPORT frame. The link margin field is set to zero in the BEACON and PROBE RESPONSE frames.
The request/report messaging and retrieving of as WTRUs physical measurement data or MAC performance statistics, such as transmit/receive power levels and link margins in as basic service set (BSS), are key parameters for supporting interference mitigation and RRM. However, these physical measurements or MAC performance statistics ere not passed from an L1 PHY or L2 MAC protocol entity to the SME, which serves as an interface to an external WLAN RRM entity. The SME typically contains interface software to read/write into the MIBs. For example, upon receiving a command from as simple network management protocol (SNMP), a read of a particular MIB entry is reported back to the SNMP.
Currently, WLANs usually transmit at a much higher power level than needed. With TPC, the transmit power can be adjusted to the minimum level to still guarantee satisfactory signal reception while not creating more interference than needed interference to other WTRUs. It is also possible to perform a effective load control and BSS range adjustments. Range adjustments, load balancing, and a maximum cell radius are determined by the transmit power of the AP and the receiver sensitivity of the WTRU. If transmit power is not properly controlled, WTRUs at the edge of the cell lose connection to the AP and will be forced to re-associate to neighboring APs. Therefore, proper power control enables effective load control and range adjustments.